Scientists use lasers to create macroscopic yarns

Published: Thursday, December 3, 2009, 14:55 [IST]

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Washington, December 3 (ANI): Scientists have used lasers to create the first practical macroscopic yarns from boron nitride fibers, opening the door for an array of applications, from radiation-shielded spacecraft to stronger body armor.

Researchers at NASA's Langley Research Center, the Department of Energy's Thomas Jefferson National Accelerator Facility and the National Institute of Aerospace created a new technique to synthesize high-quality boron-nitride nanotubes (BNNTs).

They are highly crystalline and have a small diameter. They also structurally contain few walls and are very long.

"Before, labs could make really good nanotubes that are are short or really crummy ones that are long. We've developed a technique that makes really good ones that are really long," said Mike Smith, a staff scientist at NASA's Langley Research Center.

The synthesis technique, called the pressurized vapor/condenser (PVC) method, was developed with Jefferson Lab's Free-Electron Laser and later perfected using a commercial welding laser.

In this technique, the laser beam strikes a target inside a chamber filled with nitrogen gas.

The beam vaporizes the target, forming a plume of boron gas.

A condenser, a cooled metal wire, is inserted into the boron plume. The condenser cools the boron vapor as it passes by, causing liquid boron droplets to form.

These droplets combine with the nitrogen to self-assemble into BNNTs.

Researchers used the PVC method to produce the first high-quality BNNTs that are long enough to be spun into macroscopic yarn, in this case centimeters long.

A cotton-like mass of nanotubes was finger-twisted into a yarn about one millimeter wide, indicating that the nanotubes themselves are about one millimeter long.

Fibrils of boron-nitride nanotubes are formed through the pressurized vapor/condenser method.

The nanotube fibrils are produced when the FEL laser beam strikes a target of pressed boron powder.

The number indicates laser power level in arbitrary units; about 1.5 kW in actuality. The target rotates to distribute the laser heat evenly.